Research shows that close to 60 percent of traffic accidents in Taiwan occur at a road intersection. When an emergency vehicle (e.g., an ambulance, a fire engine, a police car, etc.) is on emergency duty, warning is typically employed, such as an audible warning (e.g., siren) and/or an active visual warning (e.g., flashing light) in order to alert other road users that the emergency vehicle is approaching. However, since the emergency vehicle typically does not follow the traffic rules, with the other road users not knowing a driving direction of the emergency vehicle, accidents tend to happen.